Chris Porter has had an injection in his hip and will miss Derby's opening pre-season friendlies.
The 26-year-old will not be involved when the Rams begin their preparations at Burton on Saturday and will remain absent for the trip to Southend on Monday.
He is expected to resume training on Monday with a view to facing Bournemouth at Dean Court two days later.
Meanwhile, fellow striker Steve Davies is also set to have a knee injury assessed after sustaining the problem in training on Monday.
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